1. Field of the Invention
The present invention relates to a gas supplying head for use in a system for processing a substrate to be processed, such as a semiconductor wafer or an LCD substrate, and also to a load lock chamber using the gas supplying head. In particular, the invention relates to a gas supplying head for preventing particles from adhering to the substrate in a reduced-pressure atmosphere, and a load lock chamber using the gas supplying head.
2. Description of the Related Art
In general, a semiconductor processing system includes a processing chamber and a load lock camber (preliminary chamber) connected to the processing chamber by a gate. In the processing system, various kinds of processing gases are used, and a process is performed on a substrate such as a semiconductor wafer or an LCD substrate under a reduced-pressure. The load lock chamber generally is provided with an inert gas supplying system and an exhausting system which are connected thereto. The inner pressure of the load lock chamber can be adjusted independently of that of the processing chamber. The semiconductor processing system may have two load lock chambers, one for holding a wafer W to be processed and the other for holding a wafer W processed.
In general, a semiconductor wafer is processed as follows:
The semiconductor wafer is transferred into the load lock chamber. The gas within the load lock chamber is exhausted and replaced with a gas such that the load lock chamber has a reduced-pressure atmosphere which is substantially the same as that of the processing chamber. Then, the gate is opened, and the wafer is transferred from the load lock chamber into the processing chamber. Sequentially, the gate is closed, and the wafer is processed in the processing chamber.
After the wafer is processed, the gate is opened, and the wafer is returned to the load lock chamber. Then, the gate is closed, and the gas within the load lock chamber is exhausted and replaced with air or an inert gas, e.g. a nitrogen gas. Sequentially, the wafer is moved our of the load lock chamber.
As the inert gas or air is introduced into the load lock chamber, particles may be adhered to the surface of the wafer for two reasons. First, the gas or air introduced into the load lock chamber makes fine particles therein fly upward. Second, the introduced gas or air includes fine particles, e.g. dust.
Known as a general method for preventing particles from flying upward is a so-called "slow vent method". In the slow vent method, the valve is gradually opened so as to restrict increase of the flow velocity of gas. However, in the load lock chamber, particles fly upward the moment the valve is opened in a reduced-pressure state, in particular a greatly reduced-pressure state, even if opening of the valve is carefully adjusted. This is because at the above moment, a gas stream generates due to rapid variation of the inner pressure of the chamber, and makes the particles fly upward. Furthermore, it is impossible to prevent fine particles included in the gas from entering the chamber.